Several things are wrong. First, you didn't put spaces between things
like rho and y, where I assume you meant to multiply. Second, for a
numerical integration everything must be a number (except y and its
derivatives); so, you need to specify hbar, rho, epsilon,k, ...
Those are just the syntax issues. BTW, if you are going to use
subscripted things like y_sub_o you need to use the Notation package and
Symbolize them.
Now, your differential equation set has multiple equations for y'[x]. Is
that what you really meant? I am not sure what problem you are solving
here. Perhaps one second order differential equation with different sets
of initial conditions? I am not sure.
Kevin
hoi-su jung wrote:
> Hi,
> I am a freshman of Mathematica, I need help here...
>
> I met such problem as:
>
> NDSolve[{ y'[x] == -\[Rho]y[x], y[0] == Subscript[y, 0],
> I\[HBar] y'[x] == \[Epsilon]y[x], y[0] == Subscript[y, 0],
> y''[x] + 2 \[Rho]y'[x] + k^2 == 0, y'[0] == Subscript[g, 0]}, y, x]
> NDSolve::dvnoarg: The function y appears with no arguments.
>
> How to Handle???
>